Action man Dwayne Johnson had to get up at 3.30 ever morning to hit the gym and gobble up steak and egg whites to maintain his impressive physique for new movie Hercules.

The man-mountain spent over six months perfecting his look for the film about the world's strongest man, and he admits preparing for the part was a tiring experience of working out and eating.

His days began long before dawn with 35-minute gym sessions and then he had to consume calories before most people were awake.

He tells U.S. news show Access Hollywood, "I had a cardio machine that was inside of my hotel room, and I would just roll out of bed, I'd have my unleaded caffeine, and I'd hop on there and I'd do 35 minutes of that cardio."

Then there would be a quick stop for breakfast before he hit the gym for muscle training.

He adds, "I would go hit the gym and then I would go to set for 12 hours - it was a lot. (I did that) from day one to (day) 95. That was my schedule.

"It was the most gruelling production I had ever done by far. It was the most gruelling physical prep I had done for anything - by the way, that includes years of playing football, years of being inside a wrestling ring and years of acting."

But, while he was happy to give up his favourite junk food and treats to get in shape, he refused to stop drinking tequila.

Johnson states, "To prep as a demigod, in my opinion, is the occasional glass of tequila - sipped, not a shoot-up. We're not back at college."